Club captain Ledley watched from the dug-out as a double from Jermain Defoe sunk the Portuguese giants at the Lane.
The problem forced Ledley to miss a couple of days training last week and he wasn't risked on Saturday with the opener at Portsmouth just a week away.
In his absence, Michael Dawson and Anthony Gardner coped admirably against the considerable threat of Benny McCarthy and Jorghino.
"It's not serious," repored Martin after the Porto game. "He will play next week.
"You always have to wait and see how we cope when he's not playing because I think he's our most important player and he wasn't there.
"Porto are quick and clever but we coped - we learned a lot from the game."
Martin Jol insisted Ledley King will be fit for the start of the Premiership next weekend after he sat out Saturday's win against FC Porto.